I LOVE reaper launcher Autarchs. I don't see them near enough in lists. They do fantastically against Tau and Marines. It makes me smile that you're running two of them.
Very strong theme to your list, I really approve. The only thing I would personally change is the vyper loadouts. I'd give them all bright lances, but that's just because I've had a HECK of a hard time in 7th popping skimmers. Especially annihilation barges. Necrons seem to be pretty common in tournaments this edition.
Let us know how this goes! I'd really like to see some pics, too! It sounds like it would be good-looking on the table.
I'm a fan of the 6 pulse laser build for all lists. Eldar have so much access to the heavy weapons in their codex that you can take scatter lasers pretty much anywhere, but 5 point pulse lasers? That's a gift from Vaul Himself! However since you've already got a hunter and 3 Prisms it might be a bit overkill. Unless you maybe switch out a prism or two for night spinners? I love night spinners. everyone should have a pet night spinner.
Since you're not running any Farseers I am inclined to agree with you. Given the option though, I'd take a Farseer over mixing my roles in larger point games. Overall the addition of hornets with no further changes will only make your list stronger. I'm really interested in hearing how this list does at the tournament!
I think both have merit for sure. If you take them with dual pulse lasers maybe see if you can get a farseer to twin link them?
This is what I was referring to in my post earlier. Since he doesn't have a farseer, I don't have much of an issue with him taking scatter/pulse laser combos, but given the option I would side with you. Farseer + 12 S8 AP2 shots is gnarly.